(MONEY Magazine) – If you're booking a vacation with your kid, get out your calculator. Total costs vary by as much as 238% among five hot sun spots. It'll run you 400% more to keep your camper happy at the YMCA day camp in the Cape Cod area than the one in Lake Geneva, Wis.Group swimming lessons splash down at 79% more in Honolulu than in Lake Geneva. (Usually, lessons are sold as a series of about 45-minute sessions; we adjusted them to hourly rates.) And when your pint-size screams for ice cream, the bite is 74% more in Honolulu than on Orcas Island, Wash. --Susan Berger